1. Field of the Invention
The present invention relates to a packaging tray and, more particularly to a high-strength, reinforced molded food packaging tray for use in packaging meats, fish, poultry and other comestibles which is adapted to be utilized in conjunction with a transparent overwrap film. The inventive packaging tray is provided with a novel peripheral lip structure which will aid in preventing the collapse or fracture of the tray sidewalls in view of pressures exerted by the overwrap film when applied to the tray in an automatic tray overwrap machine. In a particularly preferred embodiment of the invention, the packaging tray is provided with a novel tray bottom wall incorporating a reinforcing structure in the form of one or more strengthening ribs which are integrated in the bottom wall of the tray.
In many modern food retailing operations, such as in supermarkets, meat and produce markets and the like, there are customarily employed many types and sizes of food trays which are usually molded from wood or paper pulp or from various plastic materials, for instance, foamed plastic, for the display and packaging of meats, fish, poultry and other produce or comestibles. Generally, these trays are relatively shallow rectangular flat-bottomed trays having outwardly inclined sidewalls, into which the commodities are placed, and thereafter a transparent heat-sealable material such as heat-shrinkable or stretchable plastic film is tightly wrapped and sealed about the tray bottom to form an attractive retail package. This type of package is extremely neat and aesthetically pleasing in appearance to a consumer, and forms a protective arrangement for the commodity contained therein while allowing the prospective customers to view its contents, so as to greatly assist in the sale of the commodities.
To a great extent, the sealing of the commodity-containing tray with the transparent overwrap film was usually effected manually by generally unskilled or semiskilled labor. Although the packages obtained in this manner are, as a rule, satisfactory in their appearance and in the quality of sealing of the commodities, the procedure was slow and cumbersome and not at all adapted to high-volume production demands.
Over the past two decades, and at an increasing percentage of the total market, there have been developed automatic tray overwrap machines which, at high rates of speed, will wrap and seal a tray containing a commodity, such as meat, fish, poultry, vegetables, or the like comestible, with a transparent overwrap film of a suitable material of the kind mentioned hereinabove. Although the automatic overwrap machines fulfill the demand for supplying wrapped trays of the type in question to a highly satisfactory degree, certain problems have been encountered in their use. Thus, the automatic overwrap machines when positioning or contacting the trays for contact with the overwrap film, and during the sealing of the film to the trays, are prone to impart relatively high forces to the sidewalls of the trays, thereby generating extremely high localized stresses which frequently cause to the tray side or end walls to buckle and fracture. This buckling may be the result of the inwardly directed forces exerted on the sidewalls of the tray due to impact by the machines and/or the surface tension imparted to the sidewalls by the overwrap film which is being applied onto the trays.
Further basic causes of tray failure when the trays are overwrapped with transparent film in automatic machines may be ascribed to poor tray design for the intended applications thereof; in essence, inadequate sidewall and tray bottom strength; incorrect design criteria in the interrelationship between the tray bottom and the upright wall structures; design of automatic equipment and the like, amongst other factors.
In essence, the failures of packaging trays while being provided with an overwrap film enclosing the comestibles on the tray in automatic tray overwrap equipment may be primarily ascribed to the following:
1. Bending or breaking at the sidewall to tray bottom transitional radius due to the concentration of inwardly or outwardly directed bending moment stresses at this point in the tray.
2. Distortion, folding or breaking of the trim lip extending about the tray resulting from the large surface film contact area of the trim flange on the tray and the high coefficient of friction between the foamed plastic tray surface with the overwrap film surface.
3. Inadequate strength and resistance to buckling of the tray bottom wall resulting from the weight of the commodity in the tray and the forces exerted thereon by the overwrap film material.
4. Bowing and resultant buckling of the trays when subjected to the wrapping forces in the equipment, and the related package instability imparted thereto by the remainder of the automated weighing/pricing/labeling equipment.
2. Discussion of the Prior Art
To some degree, the prior art has taken cognizance of the problems which are commonly encountered in the wrapping of trays with an overwrap film of the type described.
Reifers et al. U.S. Pat. No. 3,761,011 describes a food packaging tray in which the sidewalls and end walls incorporate outwardly and downwardly extending peripheral lips adapted to resist collapse of the loaded tray caused by pressure exerted by the transparent overwrap plastic film. However, the lip construction in this patent is of a rather complex configuration and would unduly increase the cost of the tray. Moreover, the Reifers tray does not appear to be constructed to withstand the high impact loads applied thereto when used in automatic tray overwrap machines.
Holden U.S. Pat. No. 4,349,146, assigned to the common assignee of the present application, discloses a molded packaging tray for the packaging of comestibles, which possesses a novel peripheral lip structure extending about the upper ends of the tray sidewalls which will aid in preventing the collapse and fracture of the sidewalls caused by pressures exerted thereon by an overwrap film when applied thereto by an automatic tray overwrap machine.
Holden U.S. Pat. No. 4,442,969, also assigned to the common assignee of the present application, pertains to a novel reinforced molded packaging tray which, in addition to a strengthened peripheral lip structure encompassing the tray sidewalls, provides for the incorporation of integral stiffening rib structure in the bottom wall of the packaging tray. This will impart further strengthening against buckling to the packaging tray, which is of particular significance to larger-sized trays, commonly referred to as family pack trays.
Although the foregoing U.S. patents, and particularly Holden U.S. Pat. Nos. 4,349,146 and 4,442,969, to a significant extent meet the needs of the industry with regard to the rapid and automated packaging of comestibles, such as meats, fish, poultry and the like, there is a need for the provision of packaging trays of this type which can satisfy the more stringent demands as to high strength which are placed on the larger sized so-called family pack trays which contain larger and resultingly heavier quantities of the commodities. This is accomplished through the provision of a novel molded packaging tray adapted for use with an overwrap film in which the peripheral lip structure on the sidewalls of the tray is configured to minimize the surface contact with the overwrap film irrespective as to whether the commodity contained in the tray exceeds or is less than the overall interior height of the packaging tray.
Pursuant to preferred embodiments of the inventive packaging tray, the latter also incorporates stiffening rib structure integrally formed in the bottom wall structure of the tray so as to still further enhance the overall strength of the packaging tray.